SLU CHEM AND PHYSICS PAGE io

Fluoride Vo1.28 N0.4 189-192 1995 Research Report 189

EFFECT OF FLUORIDE EXPOSURE OM INTELLIGENCE IN CHILDREN X S Li,a J L Zhi,b and R 0 GaoC , SUMMARY: The intelligence was measured of 907 children aged 8-13 years living in areas which differed in the amount of fluoride present in the environment. The Intelligence Quotient (IQ) of children living in areas with a medium or severe prevalence of fluarosis was lower than that of children living in areas with only slight fluorosls or no fluorosis- The development of intelligence appeared to be - adversely affected by fluoride in the areas with a medium or severe prevalence of fluorodis but to a minor extent only in areas with only a slight prevalence of fluorosis. A high fluoride intake was associated with a lower intelligenoe. No 4 c~rrelationwas found between age and intelligence in the areas with a medium and severe prevalence of fluorosis. The effect of exposure to a high level of fluoride on intelligence may oaur at an early stage of development of the embryo and infant when the tliffererrtiatian of brain newe tells is occuning and dedop- ment is most rapid- Keywords: Child; China; Fluoride; Fluorosis; Intelligence; Intelligence testing. Introduction With the study in rcccnt years of dcmic flu0 is, attention has been given to the efEct of fluoride on intelligence in ~hildren!~hthe present study children living in arwwith differing prcvalmces of fluorosis received intexligence tcsting. Materials and Methods The suhrey was carried out in November and December I99 1 in the Anshu and Zhijin counties in Guithou Province. The prevalence of fluorosis due to soot hm cdal buming varid from beqabsent to bcing present to a slight, medium or sevcre dcgrce. In thc rndium and severe fluorosis areas, it was cum~maryfor -1 to be used as a domesic firel for mdcxng, hcatirg and dxying grain whereas in &e areas Mithout or only slight flusrosis there was no custom of drying grain by tbe use of d.The standards of material and cultural life for the children we= similar in all four areas. The suwcy arcas have no iodine deficiency disease. The children suruyed were of Han nationality and numbered 907 with ages fkun 8-13 years. Children whose intelligence had been afbted by cmgmital or acquired dismses not related to fluoride were excluded. hlligencc was measured using the China Rui Wen's Scaler for Rurd 1 Areus? In each area, 20-24 children were examined, by a special examiner, in each age group dth &he groups being sepatated by intervals of six months age. i Gukhou Provincial Sanitary and Anti-Epidemic Station, City, 550001, China. Prefecture Sanitary and Anti-Epidcmk Station. Zhijin County Sa& and Anti-EpidhC Station. Presenred to the XXth Conference of the International Society for Fluoride Researc4 Sing,China Scptember 5-9. 1994. SLU CHEM AND PHYSICS PAGE 11 09/15/2004 15: 03 3152297421 190 Lief a/ Fluoride 28 (4)

The significance: of thc various Icvcls in the Intclligence Quotimt (XQ)were; <70 low; 70-79 bordcrlinc; 80-89 lower medium; 90-109 rncdiwn; 1 10-1 19 upper mcdiurn; 120-129 excellent; >I129 special excellence. The dental fluorosis index using the method of Dean and the urinary fluoridc concentrations for the children hrnthe four differenr areas are shown in Table 1.

Table 1, Dental fluorosis prevalence, dental fluorosis index and urinary fluoride concentration far children from areas with no fluorosis and slight, medium and $evere prevalences of fluorosis Non- Slight Medium. Swere c fluorosis fluomis fluorosis fluorosis area area area area Dental fluorosis (0.4 0.8 2.5 3.2 index Urinary F mg/L 1.02 1.87 2.01 2.69

Results The numbers of children examincd in each area and their mean IQs are shown ia Table 2. The distribution of the IQ sfom is shown in Table 3. As shmm in Table 3, morc children with TQs af e70 and 70-79 and fewer children vrith XQs of 90-109 and 1 10-1 19 wm present in the medium and seveE fluomis areas than in the slight fluorosis and non-fluorosis areas. No children with IQs of 120-129 and >129 were bund in the medium and sevcre fluorosis ateas- In Table 4 &e IQs of children of dffiages from afea~with diffkdg prmdena of fluorosis are Shawn. A comparison of the IQs of boys and girls is shown in Table 5. Discussion The results of the sunqshow that the intelligence, as measured by the mean IQ, of children aged 8- 13 years living in areas with a medium or severe prevalence of fluorosis was lower tban that of children living in ateas with a slight p;revdence of fluorosis or no fluorosis. Similarly more children with a low or borderline IQ wem pmmt in the medium and smfluorosis areas. That a high fluaride a- vircmment can dversely the development of intelligmce in children is ~II agreanent with the findings of Guo et d1No sigdicant difference in imebmce was present be- children in the slight fluorosis and the non-fluorosis ma. The lowering of intelligence in the moderate and severe fluorosis areas indicares that the central n~mss>Stems of the children in those arkas are advmely aff;ectcd by fluoride. Because no correlation was found bctween age and IQ hr children h the medium and severe fluorosis arr;;as, ir appears that thc influence of a high fluoride emimment on the dewlopmat of iutelligmce may -ut early in developmerrl; such as during the stagff of embryonic lifk or &cy when the differentiation and PAGE 12 09/,15/2004 15: 03 3152297421 SLU CHEM AND PHYSICS

I* November 1995 Effect on intelligence in children 791 Table 2. Numbers of children examined and their mean 10s in areas differing in the prevalence of fluorosis Non-fluorosis Slight fluorosis Medium Severe area area fluorosis area fluorosis area Number of E hildren 226 227 224 230 examined IQ ImeanaSD) 89.921 0.4* 89.7f12.7 79.7%1 2.7" 80.3fl2.W- * comparing the non-fluorosis and slight fluorosis areas t = 0.1 10, p > 0.05. *I comparing the medium and severe fluorosis areas t = 0.367, p > 0.05. - comparing the severe and medium fluorosis areas, and the slight and non-fluorosis areas t = 5.922, p 4 0.01.

Table 3. The distribution of child IQ scores from areas of differing fluorosis prevalence

~~ Fluorosis IQ IQ IQ IQ IQ IQ IQ status of area ~CJ 7P7B 8089 90-109 110.119 120-129 ,129 - ., Non 2.6% 9.7% 37.1% 46.8% 3.9% 0.8% 0 Slight 3.1% 15.9% 29.1% 47.1% 3.7% 1.3% 4.4 Medium 25.4% 23.7% 29.9% 20.5% 0.4% 0 0 Severe 20.9% 26.6% 26.9% 25.2% 0.4% 0 0

Table 4. IQs of children of different ages from areas differing in the prevalence of fluorosis IQ (meanSD) of children from areas in which the fluorosis prevalence was: Age in yearsb non-fluorosisC slight mediumd severe

~ ~~ 8.0 - 8.49 86.1211.4 90.7 f: 9.7 78.Qi13.9 83.8~14.4 8.5 - 8.99 88.W13.9 87.2f20.2 79.8210.0 80.&15.1 9.0 - 9.49' 91.121 1.2 92.6t11.1 78.7~146 82.1214.1 9.5 - 9.99 86.3511.3 88.7f126 75.8k15.6 81.9?75.2 1 6.0-1 0.498 88.4 2 8.6 92.0k13.9 81.1213.5 82.9 f 9.0 10.5-10.99a 90.6 f a.1 97.7212.6 75.5 f 9.2 79.6t1 0.5 11-0-1 1.49' 92.Z13.1 86.7 f 9-8 f7.31t11.8 75.Q? 12.3 1 1.5-11. gSa 91.75 9.5 90.1t13.4 78.4k13.5 79.6t13.5 12.0-12.49 87.4 f 5.9 88.Bf 1 0.4 85.9112.8 76.9T 14.3 12.5-1 2.9P 93.2 f 5.7 86Bi1 0.2 85.5 2 9.5 77. M2.6 13.6-13.49e 93.8 9.5 94.3i-12.7 85.5f10.6 83.If1 0.4 e camparing non-fluorosis and slight fluorosis areas, and medium and $&ere fluorosis areas t = 1 B454.81,p c 0.05.Fot other age groups comparisons were not significant. comparing the IQ for one age group with that fer other age groups in the same area. no significant differences were found t = 0.03-1.70, p > 0.05. No trend was found indicating that the IQ became lower as the time spent in a high fluorosis area Increased. comparing non-fluorosis and slight fluorosis areas, no significant dWference was found. comparing the medium and severe fluorosis areas, ne signffimnt difterence was feund. SLU CHEM AND PHYSICS PAGE 13 09/15/2004 15: 03 3152297421

192 ti et a/ Fluoride 28 (4) November 1995

Table 5. The IQs of boys and girls aged 8-13 from areas of differing fluorosis prevalence IQ (mLaniSD) of children living in areas in Hmich the prevelence of fluorosis was;

b non-fluorosis slight medium severe W’’ Boys * 89.3f0.82 89.821 10 81.21 07 80.6i1.06 (nr148) (~139) (n=l32) (n=l51) Girls Q1.6k1.26 89 4al 30 77.6k1.33 79.8kl.44 (~78) (n=08) (n=92) (n=7Q) “comparing boys and girls in each of the areas differing in fluorosis prevalence p>0.5 (Standards established for the test show no significant difference between the sexes4) f

growth of the nervous system is most rapid. A higher concentration.- of fluoride has 4 been fourld in embryonic brain tissue obtained from t- on of P=twJw operations in areas where fluorosis due to coal burning was ~reyalent,~ Stereological and ultramicroscopic srudy of this tissue showed the di&rentiation of brain nene cells was poor, and brain development was delayed. This suggests that developing brain tissues are sensitive to the toxic ef3kct.s of fluoride. The findings in the present study suggest that in areas with a medium or severe prevalance of fluorosis, active and comprehensive matsums should be taken to reduce the fluoride intake fbr the population, especially in pregnant women and infants. Avoiding a high intake of fluoride is seen to be a important factor in determining the quality of health cnjoyd by ammunities. Aclmowledgement The authors thank sincxxdy Pmf’essor Wang-Dong, Tian Jin Medical CoIlcge for his belp with the study and manuscript. References Guo XC, WagRY, Chen CF. A pe- exploration of IQ of 7-13 year old pupils in a fluorosis area with amtamination hmburning caal. Chinese Journul of Conhl crfEndemic Diseuses 10 (2) 98-100 1991 [Ianguage Chinese]. Qin LS. Oii SY. The influence of drinldng water fluoride on pupils’ IQ as measured by Rui Wen’s Standards. Chinese Journal oJContr01 of Epidemic Diseases 5 (4) 203-204 1990 [language Chinese].. Manual ofdntiepidemic Fhwosis. Bureau of hticpidemic DisraseS of lvfirmq of public Wth. Win1989 [language Chinese). Insrmct/on book on combined of Rui Uhn ’s Test Tian-Jin Medical College. 1989 Oanguagc Chinese]- He K Chen ZS, Liu XM The innuen~mof fluoridc on rhe human embryo. Chinese t Journal of Control of Epidemic Diseuses 4 136- 13 7 1 989 [language Chinese). Du L, Wan CW,Cao XM The influence of chronic 5uorosis on the dmlopmmt of the brain ofthe human embryo. Journal of Fluorosis Research Comrnvnicahons 138 1991 * [language Chinese].

Published by the International Society for Fluaride Research Editorial Office: 81A Landscape Road, Mount Eden, Auckland 4. New Zealand